Just saw this! Rereading in a different format is already covered by the app, but we need to work on the other style of reading. Merging this post into a related feature request!

I've never done it before but coincidentally a book I had on hold in both audiobook and ebook became available simultaneously on Libby so I'm trying out a DIY "Whispersynch" by switching back and forth. I chose to just mark progress in the ebook but it is an interesting thought!